Proton radiotherapy is growing in the US and around the world. This growth is due to the commercial availability of protons and the physical advantages of the improved ability to deposit most of the radiation dose in the tumor, as opposed to x-rays where most of the dose is deposited in normal tissues. In the US there are currently five proton therapy centers treating patients and over 2300 x-ray based linear accelerator facilities. Limiting the widespread application of proton radiotherapy to the general cancer patient community is the capital, building and operating costs associated with proton radiotherapy that exceed $100 million per site, a substantial cost differential with x-ray based facilities. A compelling approach is to combine the physical advantages of proton therapy into a smaller, cheaper, gantry-mounted or fixed line system that can be widely disseminated for improved radiotherapy. The development and investigation of such an approach using coaxial plasma proton acceleration, is described in this proposal. Recent breakthroughs in the understanding and stabilization of a special high-velocity mode of operation in plasma accelerators by the Plasma Physics Laboratory at Stanford University have lead to an accelerator concept with the potential to make affordable, compact proton therapy possible. The aims for this feasibility study are to develop the existing accelerator to: 1. Testing and beam characterization: This task includes the use of various optical diagnostics and the measurements of phase space properties using a magnetic sector energy spectrometer. Nuclear track detection is used as a contingency to characterize the beam over a wide range of operating conditions. 2. Increase plasma accelerator beam energy: This task consists of optimization and scaling of various parameters, such as electrode shapes and dimensions, electric circuit parameters, mass flow, and power supply voltage. This task also includes the development of a new hydrogen injection system. 3. Modeling of beam dynamics: The feasibility of using a compact magnet/collimator assembly for energy dispersion and selection is assessed using the Geant4 software. The goal is to study approaches for beam transport and collimation while minimizing and capturing harmful secondary radiation and neutrons. The long term goal of this project is to develop the next generation of proton therapy treatment units that will improve human health through the wide dissemination of a compact, single room, proton therapy treatment system. PUBLIC HEALTH RELEVANCE: This proposal describes a high-impact, high risk development combining exciting cutting edge developments in accelerator technology in mechanical engineering at Stanford University with an important unmet need in radiation oncology- a relatively compact, inexpensive accelerator for proton therapy. The long term goal of this project is to develop the next generation of proton therapy treatment units that will improve human health of cancer patients by the wide dissemination of a small, single room, proton therapy treatment system that will allow increased access to this improved treatment modality.